The serial port is locked out everytime when the matlab code reads it. For executing the code again, I need to remove and reconnect the Uno microcontroller back to my computer. My OS is Ubunbtu 14.04.

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Melvin Manuel 2019-12-28

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/498302-the-serial-port-is-locked-out-everytime-when-the-matlab-code-reads-it-for-executing-the-code-again

评论： Melvin Manuel 2020-4-14

I have written a simple MATLAB code to read the serial port. An arduino UNO microcontroller is continuously sending some data to the USB port. For example /dev/ttyUSB6. When I run the MATLAB code, the code runs once witout any issues. But when I execute the code again I am getting a error message as follows..

Error using serial/fopen (line 72)

Open failed: Port: /dev/ttyUSB6 is not available. Available ports: /dev/ttyUSB1.

Use INSTRFIND to determine if other instrument objects are connected to the requested device.

Error in Serial_dec23 (line 18)

fopen(s);

At the same time in MATLAB terminal, I can see another error message as follows

RXTX fhs_lock() Error: opening lock file: /var/lock/LCK..ttyUSB6: File exists

If I need to run the code again, I need to remove the microcontroller board and re-connect it back and then update the USB port number in my MATLAB code to /dev/ttyUSB7. Then, again it will succesfully run once and agian will be locked out.

How can I solve this lock out issue? I tried deleting the lock file available inside /var/lock folder. But it didn't helped me to resove the issue.

The basic code to read the serial port that I used is as follows

clc;
clear all;
close all;
instrfind()
bR=115200;
 
s=serial('/dev/ttyUSB6','BaudRate',bR);
 
fopen(s);
    
    for i = 1:2
        an = fscanf(s,'%c');
                   
    end
 
C = strsplit(an,';');
t1 = cell2mat(C(1));
fclose(s);
delete(s);
clear s;

Could you please help me to resolve this. I just need to read the USB port contineously without removing and reconnecting the microcontroller board everytime